The present invention relates to a check valve assembly, particularly for aggressive media, and a method of manufacturing the same. More particularly, it relates to a check valve assembly which has a housing, and a throttle valve which includes a throttling disc rotatable in the housing and a spindle guided in the housing and rotating the throttling disc.
Check valves of the above-mentioned general type are known in the art. The throttling disc of such a check valve may be arranged centrally or eccentrically. The check valve may have a one-piece or two-piece outer ring. The spindle or journals may be cast on or welded to the throttling disc or may loosely extend through the latter. Various embodiments of this check valve depend more or less on different applications or respective manufacturing possibilities. When such check valves are utilized in an aggressive medium, it is necessary to manufacture all parts of the check valve, which in operation are in contact with the aggressive medium, from a material which resists the deleterious action of the latter. It has been proposed to manufacture the throttling disc from a synthetic plastic material or to coat the throttling disc by this material. It is also known to manufacture the protective lining connected with the housing of the check valve, from an elastomeric or another suitable material. In the check valves in which the throttling disc is coated by a synthetic plastic material, this coating extends only to the transition area between the throttling disc and the spindle connected to the latter. The protective lining of the housing also extends only somewhat into the above-mentioned transition area.
However, during the rotary movement of the throttle valve, for example, as a result of the sliding movement, small quantities of the medium leak or diffuse through or between the seals so that in operation with aggressive media undesirable and detrimental corrosion takes place. It has been recognized that this corrosion can be avoided by inserting special seals and/or utilizing corrosion-resistant fine steel for the parts of the check valve which are in contact with the aggressive media during the operation. In spite of these measures which are relatively expensive in the sense of the construction and material consumption, the results have not been satisfactory.